1. Field of the Invention
The present invention generally relates to the control of the access to resources exploited by a microprocessor. More specifically, the present invention relates to the control of the access to peripherals exploited by at least one main processor according to the applications (software) executed by this microprocessor and to the rights of access which are respectively granted thereto.
2. Discussion of the Related Art
“Microprocessor peripheral” is used to designate a physical device communicating with a microprocessor over a bus and used, most often, as an interface with another device (for example, a network connection, a graphics board, a keyboard, a memory, etc.).
The development of communicating computer systems and of program downloads over communication networks which are not necessarily secure has caused problems in the execution of programs by processor systems. Among these problems, the present invention more specifically relates to those linked to the access given to peripherals of the system in unauthorized fashion by programs. Indeed, despite all authentication, cryptography, and systems which currently control authenticity or the validity of a program loaded in the memory of a processor system, there remains a risk of fraudulent or incidental attempt of access by the program to resources of the system in which it has been validly installed.
An example of an application of the present invention relates to mobile systems of a GSM type. In such an application, the user authentication is performed via its smart card (SIM card) which contains information such as an access key to the GSM network. With the development of telephone devices that are becoming more and more open in terms of executable applications (communicating computers, PDA, etc.), an application is likely to have access to telephone resources which are not intended for it. Such an access may result, for instance, in an incidental or voluntary blocking of the SIM card without this to have been desired by the user or the operator, or yet during an access to another parallel network (wireless local area network—WLAN—or the like) with no control by the GSM operator. Further, this makes systems more vulnerable to viruses or pirate access.
Another example application of the present invention relates to broadcast signal receivers/decoders (set top boxes) which allow viewing by a television set of certain signals received according to a key contained in a smart card, and defining the channels accessible by the user. The smart card is used to decipher the data or to provide the access key to the data formed by the diffused programs. The decoder also enables downloading applications, such applications being likely to come from sources uncontrolled by the operator (for example, the Internet). However, all the internal resources of the decoder are then potentially accessible to these applications, which is a weakness in terms of system security.